DESCRIPTION: The focus of this project is on the potential of tannins (found in many fruits and vegetables) to serve as biological antioxidants. The investigators hypothesizes that the role of tannins is to "spare" nutritive antioxidants in the gastrointestinal tract. They plan to evaluate this hypothesis by determining the effect of dietary tannins on plasma antioxidant levels in rats. The in vivo studies will be complemented by ex vivo studies of the effect of tannins on oxidative reactions in gastrointestinal tract fluid. The ability of various tannins to provide antioxidant protection will be assessed by measuring lifetimes of nutritive antioxidants in GI tract fluids containing specific tannins of interest. Susceptibility of proteins and lipids in the GI tract to oxidative damage in the presence and absence of tannin will also be measured. These studies should provide the basis for understanding which types of tannins influence antioxidant levels. Ultimately the data could provide a scientific basis for recommending certain fruits and vegetables.